Nuclear Theory·nucl-th

Tuesday·December 30, 2014

15 papers—7 primary·8 cross-listed

01
Effects of quark chemical equilibration on thermal photon elliptic flow
Akihiko Monnai🇺🇸
Large hadronic elliptic flow $v_{2}$ is considered as an evidence for the existence of a strongly-coupled QGP fluid in high-energy heavy-ion collisions. On the other hand, direct photon $v_{2}$ has recently been found to be much larger than hydrodynamic estimations, which is recognized as "photon $v_{2}$ puzzle". In this study, I discuss the implication of late production of quarks in an initially gluon-rich medium because photons are coupled to quarks. Numerical analyses imply that thermal photon $v_{2}$ can be visibly enhanced. This indicates that interplay of equilibration processes and collective expansion would be important.
nucl-thJ.Phys.Conf.Ser.(2015)·3 citations
02
Topics in Low-Energy QCD with Strange Quarks
Wolfram Weise🇩🇪
Recent developments and pending issues in low-energy strong interaction physics with strangeness are summarized. Chiral SU(3) effective field theory has progressed as the appropriate theoretical framework applied to antikaon- and hyperon-nuclear systems. Topics include antikaon-nucleon interactions and the Lambda(1405), KbarNN systems, recent developments in hyperon-nucleon interactions and strangeness in dense baryonic matter with emphasis on new constraints from neutron star observations.
nucl-thHyperfine Interact.(2015)·15 citations
03
Searching for isovector signatures in the neutron-rich oxygen and calcium isotopes
Wei-Chia Chen · J. Piekarewicz
We search for potential isovector signatures in the neutron-rich oxygen and calcium isotopes within the framework of a relativistic mean-field theory with an exact treatment of pairing correlations. To probe the isovector sector we calibrate a few relativistic density functionals using the same isoscalar constraints but with one differing isovector assumption. It is found that under certain conditions, the isotopic chain in oxygen can be made to terminate at the experimentally observed $^{24}$ O isotope and in the case of the calcium isotopes at $^{60}$ Ca. To produce such behavior, the resulting symmetry energy must be soft, with predicted values for the symmetry energy and its slope at saturation density being $J = (30.92 \pm 0.47)$ MeV and $L = (51.0 \pm 1.5)$ MeV, respectively. As a consequence, the neutron-skin thickness of $^{208}$ Pb is rather small: $R_{skin}^{208} = (0.161 \pm 0.011)$ fm. This same model - labelled "FSUGarnet" - predicts $R_{1.4} = (13.1 \pm 0.1)$ km for the radius of a "canonical" 1.4 $M_{⊙}$ neutron star, yet is also able to support a two-solar-mass neutron star.
nucl-thnucl-exPLB(2015)·148 citations
04
Theoretical investigation of the decay of the $N (2120)$ resonance to nucleon resonances near 1.7 GeV
Yin Huang🇨🇳 · Jun He🇨🇳 · Xu-Rong Chen🇨🇳 · Rong Wang🇨🇳 · Jun-Jun Xie🇨🇳 · Hong-Fei Zhang🇨🇳
Background: Until now the knowledge about nucleon resonances with a mass higher than 2 GeV has been scarce. Huge amounts of experimental data of the multipion photoproduction have been accumulated, and more can be expected in the future in facilities such as JLab 12 GeV. It makes it possible to investigate the decay of a nucleon resonance into another nucleon resonance. Purpose: The possibility to research the decay of the $N (2120)$ to nucleon resonances near 1.7 GeV in the three-pion photoproduction will be explored to provide useful information for future experimental study. Method: The pion and radiative decay amplitudes of nucleon resonances are studied within the constituent quark model, which is used to calculate the couplings constants, especially for the decay of a nucleon resonance near 2.1 GeV to another nucleon resonance near 1.7 GeV. The three-pion photoproduction off the neutron target, i.e., $γ n \to π^{-} π^{-} Δ^{++} \to π^{-} π^{-} π^{+} p$ , is investigated based on the effective Lagrangian method with the coupling constant obtained form the decay amplitudes. Results: The resonance contribution with a state $N (^{2} P_{M}) \frac{3}{2}^{-}$ near 2.1 GeV decaying to a state $N (^{4} P_{M}) \frac{5}{2}^{-}$ near 1.7 GeV, i.\ e., $N (2120) \to N (1675) π$ is dominant in the process considered. The total cross section from the resonance contribution is at the order of 1 $μ$ b and can be easily distinguished from the background. Conclusions: Our results suggest it is practicable to research the decay of the $N (2120)$ to the $N (1675)$ in experiment.
nucl-thhep-phnucl-exPRC(2015)·2 citations
05
Nuclear response theory with multiphonon coupling in a covariant framework
Elena Litvinova
Background: Nuclear excited states within a wide range of excitation energies are formally described by the linear response theory. Besides its conventional formulation within the quasiparticle random phase approximation (QRPA) representing excited states as two correlated quasiparticles (2q), there exist extensions for 4q configurations. Such extended approaches are quite successful in the description of gross properties of nuclear spectra, however, accounting for many of their fine features requires further extension of the configuration space. Purpose: This work aims at the development of an approach which is capable of such an extension as well as of reproducing and predicting fine spectral properties, which are of special interest at low energies. Method: The method is based on the covariant density functional theory and time blocking approximation, which is extended for couplings between quasiparticles and multiphonon excitations. Results: The covariant multiphonon response theory is developed and adopted for nuclear structure calculations in medium-mass and heavy nuclei. The equations are formulated in both general and coupled forms in the spherical basis. Conclusions: The developed covariant multiphonon response theory represents a new generation of the approaches to nuclear response, which aims at a unified description of both high-frequency collective states and low-energy spectroscopy in medium-mass and heavy nuclei.
nucl-thPRC(2015)·34 citations
06
Analysis of proton and neutron pair breakings: High-spin structures of $^{124 - 127}$ Te isotopes
Vikas Kumar · P.C. Srivastava · M. J. Ermamatov · Irving O. Morales
In the present work recently available experimental data for high-spin states of four nuclei, $_{52}^{124}$ Te, $_{52}^{125}$ Te, $_{52}^{126}$ Te, and $_{52}^{127}$ Te have been interpreted using state-of-the-art shell model calculations. The calculations have been performed in the $50 - 82$ valence shell composed of $1 g_{7/2}$ , $2 d_{5/2}$ , $1 h_{11/2}$ , $3 s_{1/2}$ , and $2 d_{3/2}$ orbitals. We have compared our results with the available experimental data for excitation energies and transition probabilities, including high-spin states. The results are in reasonable agreement with the available experimental data. The wave functions, particularly, the specific proton and neutron configurations which are involved to generate the angular momentum along the yrast lines are discussed. We have also estimated overall contribution of three-body forces in the energy level shifting. Finally, results with modified effective interaction are also reported.
nucl-thNPA(2015)·11 citations
07
Pairing properties and specific heat of the inner crust of a neutron star
A. Pastore
We investigate the pairing properties at finite temperature of the Wigner-Seitz cells in the inner crust of a neutron star obtained with the recent Brussels-Montreal Skyrme functional BSk21. In particular we analyze the phenomena of persistence and reentrance of pairing correlations and their impact on the specific heat in the low-density region of the inner crust.
nucl-thastro-ph.SRPRC(2015)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE

Effects of quark chemical equilibration on thermal photon elliptic flow

Topics in Low-Energy QCD with Strange Quarks

Searching for isovector signatures in the neutron-rich oxygen and calcium isotopes

Theoretical investigation of the decay of the N(2120) resonance to nucleon resonances near 1.7 GeV

Nuclear response theory with multiphonon coupling in a covariant framework

Analysis of proton and neutron pair breakings: High-spin structures of 124−127Te isotopes

Pairing properties and specific heat of the inner crust of a neutron star

Affiliations

Theoretical investigation of the decay of the $N (2120)$ resonance to nucleon resonances near 1.7 GeV

Analysis of proton and neutron pair breakings: High-spin structures of $^{124 - 127}$ Te isotopes